08Click-to-load embed — a placeholder that recomputes the size delta to grow smoothly

<main class="stage">
<section class="panel">
  <div class="card" id="card">
    <div class="placeholder" id="placeholder" role="button" tabindex="0" aria-label="Load play item" aria-pressed="false">
      <span class="playIcon" aria-hidden="true"></span>
      <span class="phLabel">Press to load</span>
      <span class="phSub">Saves about 0.5MB</span>
      <span class="hintArrow" id="hintArrow" aria-hidden="true"></span>
    </div>
    <div class="frame" id="frame" aria-hidden="true">
      <canvas class="frameThumb" id="frameThumb" width="240" height="120"></canvas>
      <div class="frameScrim"></div>
      <div class="frameContent">
        <span class="framePlay" aria-hidden="true"></span>
        <span class="frameLabel">Loaded video frame</span>
      </div>
      <div class="progressTrack">
        <div class="progressBar" id="progressBar"></div>
      </div>
    </div>
  </div>
  <div class="readout" id="readout" aria-live="polite">
    <span class="readoutLabel">Current height</span>
    <span class="readoutValue" id="heightValue">0px</span>
  </div>
</section>
</main>

@use "../../../../site/static/demo-tokens" as *;

@include stage($stage-paper);

.panel {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-3;
}

.card {
  position: relative;
  box-sizing: border-box;
  width: 240px;
  overflow: hidden;
  border-radius: $r-control;
}

.placeholder {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-1;
  box-sizing: border-box;
  width: 100%;
  padding: $sp-4 $sp-3;
  border-radius: $r-control;
  background: $subject-cream;
  color: $subject-ink;
  cursor: pointer;
}

.playIcon {
  width: 0;
  height: 0;
  margin-bottom: $sp-1;
  border-top: 8px solid transparent;
  border-bottom: 8px solid transparent;
  border-left: 14px solid $subject-ink;
}

.phLabel {
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  font-weight: 600;
  font-size: 13px;
  line-height: 1.3;
}

.phSub {
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  font-weight: 400;
  font-size: 11px;
  line-height: 1.3;
  opacity: .72;
}

.hintArrow {
  width: 0;
  height: 0;
  margin-top: $sp-1;
  border-left: 6px solid transparent;
  border-right: 6px solid transparent;
  border-top: 8px solid $subject-ink;
  opacity: .86;
}

.frame {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
  opacity: 0;
  border-radius: $r-control;
  overflow: hidden;
}

.frameThumb {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  display: block;
}

.frameScrim {
  position: absolute;
  inset: 0;
  background: rgba($stage-ink, .68);
}

.frameContent {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: $sp-2;
  color: $subject-cream;
}

.framePlay {
  width: 0;
  height: 0;
  border-top: 9px solid transparent;
  border-bottom: 9px solid transparent;
  border-left: 16px solid $subject-cream;
}

.frameLabel {
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.3;
}

.progressTrack {
  position: relative;
  width: 100%;
  height: 4px;
  background: rgba($subject-cream, .24);
}

.progressBar {
  height: 100%;
  width: 100%;
  transform-origin: left center; // 채움 막대가 시작 변에서 자라난다 (BD8 예외 대상)
  transform: scaleX(0);
  background: $subject-cream;
}

.readout {
  display: flex;
  align-items: center;
  gap: $sp-2;
  padding: $sp-1 $sp-3;
  border-radius: $r-pill;
  background: $subject-blue-deep;
  color: $subject-cream;
}

.readoutLabel {
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  font-weight: 500;
  font-size: 11px;
  line-height: 1.3;
  opacity: .84;
}

.readoutValue {
  font-family: "Space Mono", ui-monospace, monospace;
  font-weight: 700;
  font-size: 13px;
  line-height: 1.3;
}

@media (max-width: 340px) {
  .panel { gap: $sp-2; }
  .card { width: 200px; }
  .placeholder { padding: $sp-3 $sp-2; }
  .phLabel { font-size: 12px; }
  .phSub { font-size: 10px; }
  .frameLabel { font-size: 11px; }
  .readoutLabel { font-size: 10px; }
  .readoutValue { font-size: 11px; }
}

@media (prefers-reduced-motion: reduce) {
  .hintArrow { opacity: .86; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffffff;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.panel {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}

.card {
  position: relative;
  box-sizing: border-box;
  width: 240px;
  overflow: hidden;
  border-radius: 12px;
}

.placeholder {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  box-sizing: border-box;
  width: 100%;
  padding: 16px 12px;
  border-radius: 12px;
  background: #fff7e6;
  color: #17141a;
  cursor: pointer;
}

.playIcon {
  width: 0;
  height: 0;
  margin-bottom: 4px;
  border-top: 8px solid transparent;
  border-bottom: 8px solid transparent;
  border-left: 14px solid #17141a;
}

.phLabel {
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  font-weight: 600;
  font-size: 13px;
  line-height: 1.3;
}

.phSub {
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  font-weight: 400;
  font-size: 11px;
  line-height: 1.3;
  opacity: 0.72;
}

.hintArrow {
  width: 0;
  height: 0;
  margin-top: 4px;
  border-left: 6px solid transparent;
  border-right: 6px solid transparent;
  border-top: 8px solid #17141a;
  opacity: 0.86;
}

.frame {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
  opacity: 0;
  border-radius: 12px;
  overflow: hidden;
}

.frameThumb {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  display: block;
}

.frameScrim {
  position: absolute;
  inset: 0;
  background: rgba(23, 20, 26, 0.68);
}

.frameContent {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 8px;
  color: #fff7e6;
}

.framePlay {
  width: 0;
  height: 0;
  border-top: 9px solid transparent;
  border-bottom: 9px solid transparent;
  border-left: 16px solid #fff7e6;
}

.frameLabel {
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.3;
}

.progressTrack {
  position: relative;
  width: 100%;
  height: 4px;
  background: rgba(255, 247, 230, 0.24);
}

.progressBar {
  height: 100%;
  width: 100%;
  transform-origin: left center;
  transform: scaleX(0);
  background: #fff7e6;
}

.readout {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 4px 12px;
  border-radius: 999px;
  background: #0a4fe8;
  color: #fff7e6;
}

.readoutLabel {
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  font-weight: 500;
  font-size: 11px;
  line-height: 1.3;
  opacity: 0.84;
}

.readoutValue {
  font-family: "Space Mono", ui-monospace, monospace;
  font-weight: 700;
  font-size: 13px;
  line-height: 1.3;
}

@media (max-width: 340px) {
  .panel {
    gap: 8px;
  }
  .card {
    width: 200px;
  }
  .placeholder {
    padding: 12px 8px;
  }
  .phLabel {
    font-size: 12px;
  }
  .phSub {
    font-size: 10px;
  }
  .frameLabel {
    font-size: 11px;
  }
  .readoutLabel {
    font-size: 10px;
  }
  .readoutValue {
    font-size: 11px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .hintArrow {
    opacity: 0.86;
  }
}

// 클릭으로 불러오는 지연 임베드(08) — 자리표시를 실측한 높이를 기준으로
// easeOutCubic 보간해 카드 높이를 계산으로 늘린다. 실키·실서버 요청 없음.
// 클릭 시 즉시 펼침(실사용자 리스너 있음).
(function () {
  var cardEl = document.getElementById('card');
  var placeholderEl = document.getElementById('placeholder');
  var frameEl = document.getElementById('frame');
  var frameThumbEl = document.getElementById('frameThumb');
  var hintArrowEl = document.getElementById('hintArrow');
  var progressBarEl = document.getElementById('progressBar');
  var heightValueEl = document.getElementById('heightValue');
  if (!cardEl || !placeholderEl || !frameEl || !frameThumbEl || !hintArrowEl || !progressBarEl || !heightValueEl) return;
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var NARROW = window.matchMedia('(max-width: 340px)').matches;

  var CYCLE_MS = 2000;
  var PRESS_AT = 900;
  var EXPAND_MS = 500;
  var FRAME_H = NARROW ? 128 : 168;
  var HINT_MS = 700;

  function mulberry32(seed) {
    var a = seed >>> 0;
    return function () {
      a |= 0; a = (a + 0x6D2B79F5) | 0;
      var t = Math.imul(a ^ (a >>> 15), 1 | a);
      t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t;
      return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
    };
  }

  function drawSeedThumb(canvas, seed) {
    var ctx = canvas.getContext('2d');
    if (!ctx) return;
    var rnd = mulberry32(seed);
    var w = canvas.width, h = canvas.height;
    var hues = [216, 32, 268, 168];
    ctx.fillStyle = 'hsl(' + hues[Math.floor(rnd() * hues.length)] + ', 38%, 22%)';
    ctx.fillRect(0, 0, w, h);
    for (var i = 0; i < 6; i++) {
      var cx = rnd() * w, cy = rnd() * h, r = (0.18 + rnd() * 0.3) * Math.min(w, h);
      ctx.fillStyle = 'hsla(' + hues[Math.floor(rnd() * hues.length)] + ', ' + (44 + rnd() * 22).toFixed(1) + '%, ' + (38 + rnd() * 26).toFixed(1) + '%, .5)';
      ctx.beginPath(); ctx.arc(cx, cy, r, 0, Math.PI * 2); ctx.fill();
    }
    ctx.fillStyle = 'rgba(255, 247, 230, .06)';
    for (var j = 0; j < h; j += 4) ctx.fillRect(0, j, w, 1);
  }

  function easeOutCubic(p) { return 1 - Math.pow(1 - p, 3); }

  drawSeedThumb(frameThumbEl, 108);

  var pressed = false;
  var pressTime = null;
  var pressAtOverride = false;
  var phH = 0;
  var prevT = 0;

  function enterPressed(t) {
    pressed = true;
    pressTime = t;
    pressAtOverride = false;
    phH = placeholderEl.offsetHeight;
    placeholderEl.setAttribute('aria-pressed', 'true');
  }

  placeholderEl.addEventListener('click', function () {
    pressAtOverride = true;
  });
  placeholderEl.addEventListener('keydown', function (e) {
    if (e.key === 'Enter' || e.key === ' ') {
      e.preventDefault();
      pressAtOverride = true;
    }
  });

  function resetToIdle() {
    pressed = false;
    pressTime = null;
    pressAtOverride = false;
    phH = 0;
    cardEl.style.height = '';
    frameEl.style.opacity = '0';
    progressBarEl.style.transform = 'scaleX(0)';
    placeholderEl.setAttribute('aria-pressed', 'false');
  }

  // 계산 겹: 자리표시의 실측 height(phH)에서 FRAME_H 까지 easeOutCubic 으로 보간해
  // 카드 높이를 계산한다. 절반을 넘으면 실 프레임이 페이드로 등장하고,
  // 펼침이 끝난 뒤엔 남은 시간 동안 진행 바가 채워진다.
  function apply(t) {
    var h;
    var hintOpacity = 0.86 + 0.14 * Math.sin(2 * Math.PI * t / HINT_MS);
    if (!pressed) {
      h = placeholderEl.offsetHeight;
      cardEl.style.height = h + 'px';
      hintArrowEl.style.opacity = hintOpacity.toFixed(3);
    } else {
      var elapsed = t - pressTime;
      if (elapsed < 0) elapsed += CYCLE_MS;
      var delta = FRAME_H - phH;
      var p = easeOutCubic(Math.min(1, elapsed / EXPAND_MS));
      h = phH + delta * p;
      cardEl.style.height = h.toFixed(1) + 'px';
      var frameOpacity = p <= 0.55 ? 0 : Math.min(1, (p - 0.55) / 0.45);
      frameEl.style.opacity = frameOpacity.toFixed(3);
      var sweepSpan = CYCLE_MS - PRESS_AT - EXPAND_MS;
      var sweepP = Math.max(0, Math.min(1, (elapsed - EXPAND_MS) / sweepSpan));
      progressBarEl.style.transform = 'scaleX(' + sweepP.toFixed(3) + ')';
    }
    heightValueEl.textContent = 'height ' + Math.round(h) + 'px';
  }

  if (reduce) {
    apply(0);
    return;
  }

  var start = null;
  function loop(ts) {
    if (start === null) start = ts;
    var raw = ts - start;
    var t = raw % CYCLE_MS;
    if (t < prevT) resetToIdle();
    prevT = t;
    if (!pressed && (pressAtOverride || t >= PRESS_AT)) enterPressed(t);
    apply(t);
    requestAnimationFrame(loop);
  }
  requestAnimationFrame(loop);
})();

import { useEffect, useRef } from "react";
import styles from "./EmbedLazyClickToLoad.module.scss";

// 클릭으로 불러오는 지연 임베드 — 자리표시의 실측 높이를 기준으로
// easeOutCubic 보간해 카드 높이를 계산으로 늘린다. 실키·실서버 요청 없음.
// 클릭 시 즉시 펼침(실사용자 리스너 있음).
const CYCLE_MS = 2000;
const PRESS_AT = 900;
const EXPAND_MS = 500;
const HINT_MS = 700;

function mulberry32(seed: number) {
  let a = seed >>> 0;
  return function () {
    a |= 0;
    a = (a + 0x6d2b79f5) | 0;
    let t = Math.imul(a ^ (a >>> 15), 1 | a);
    t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t;
    return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
  };
}

function drawSeedThumb(canvas: HTMLCanvasElement, seed: number) {
  const ctx = canvas.getContext("2d");
  if (!ctx) return;
  const rnd = mulberry32(seed);
  const w = canvas.width;
  const h = canvas.height;
  const hues = [216, 32, 268, 168];
  ctx.fillStyle = "hsl(" + hues[Math.floor(rnd() * hues.length)] + ", 38%, 22%)";
  ctx.fillRect(0, 0, w, h);
  for (let i = 0; i < 6; i++) {
    const cx = rnd() * w;
    const cy = rnd() * h;
    const r = (0.18 + rnd() * 0.3) * Math.min(w, h);
    ctx.fillStyle =
      "hsla(" +
      hues[Math.floor(rnd() * hues.length)] +
      ", " +
      (44 + rnd() * 22).toFixed(1) +
      "%, " +
      (38 + rnd() * 26).toFixed(1) +
      "%, .5)";
    ctx.beginPath();
    ctx.arc(cx, cy, r, 0, Math.PI * 2);
    ctx.fill();
  }
  ctx.fillStyle = "rgba(255, 247, 230, .06)";
  for (let j = 0; j < h; j += 4) ctx.fillRect(0, j, w, 1);
}

function easeOutCubic(p: number) {
  return 1 - Math.pow(1 - p, 3);
}

export default function EmbedLazyClickToLoad() {
  const cardRef = useRef<HTMLDivElement>(null);
  const placeholderRef = useRef<HTMLDivElement>(null);
  const frameRef = useRef<HTMLDivElement>(null);
  const frameThumbRef = useRef<HTMLCanvasElement>(null);
  const hintArrowRef = useRef<HTMLSpanElement>(null);
  const progressBarRef = useRef<HTMLDivElement>(null);
  const heightValueRef = useRef<HTMLSpanElement>(null);
  const pressAtOverrideRef = useRef(false);

  useEffect(() => {
    const card = cardRef.current;
    const placeholder = placeholderRef.current;
    const frame = frameRef.current;
    const frameThumb = frameThumbRef.current;
    const hintArrow = hintArrowRef.current;
    const progressBar = progressBarRef.current;
    const heightValueEl = heightValueRef.current;
    if (!card || !placeholder || !frame || !frameThumb || !hintArrow || !progressBar || !heightValueEl) return;
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    const narrow = window.matchMedia("(max-width: 340px)").matches;
    const FRAME_H = narrow ? 128 : 168;

    drawSeedThumb(frameThumb, 108);

    let pressed = false;
    let pressTime = 0;
    let phH = 0;
    let prevT = 0;

    function enterPressed(t: number) {
      pressed = true;
      pressTime = t;
      pressAtOverrideRef.current = false;
      phH = placeholder!.offsetHeight;
      placeholder!.setAttribute("aria-pressed", "true");
    }

    function resetToIdle() {
      pressed = false;
      phH = 0;
      card!.style.height = "";
      frame!.style.opacity = "0";
      progressBar!.style.transform = "scaleX(0)";
      placeholder!.setAttribute("aria-pressed", "false");
    }

    // 계산 겹: 자리표시의 실측 높이(phH)에서 FRAME_H 까지 easeOutCubic 으로 보간해
    // 카드 높이를 계산한다. 절반을 넘으면 실 프레임이 페이드로 등장하고,
    // 펼침이 끝난 뒤엔 남은 시간 동안 진행 바가 채워진다.
    function apply(t: number) {
      let h: number;
      const hintOpacity = 0.86 + 0.14 * Math.sin((2 * Math.PI * t) / HINT_MS);
      if (!pressed) {
        h = placeholder!.offsetHeight;
        card!.style.height = h + "px";
        hintArrow!.style.opacity = hintOpacity.toFixed(3);
      } else {
        let elapsed = t - pressTime;
        if (elapsed < 0) elapsed += CYCLE_MS;
        const delta = FRAME_H - phH;
        const p = easeOutCubic(Math.min(1, elapsed / EXPAND_MS));
        h = phH + delta * p;
        card!.style.height = h.toFixed(1) + "px";
        const frameOpacity = p <= 0.55 ? 0 : Math.min(1, (p - 0.55) / 0.45);
        frame!.style.opacity = frameOpacity.toFixed(3);
        const sweepSpan = CYCLE_MS - PRESS_AT - EXPAND_MS;
        const sweepP = Math.max(0, Math.min(1, (elapsed - EXPAND_MS) / sweepSpan));
        progressBar!.style.transform = "scaleX(" + sweepP.toFixed(3) + ")";
      }
      heightValueEl!.textContent = "높이 " + Math.round(h) + "px";
    }

    if (reduce) {
      apply(0);
      return;
    }

    let start: number | null = null;
    let raf = 0;
    function loop(ts: number) {
      if (start === null) start = ts;
      const raw = ts - start;
      const t = raw % CYCLE_MS;
      if (t < prevT) resetToIdle();
      prevT = t;
      if (!pressed && (pressAtOverrideRef.current || t >= PRESS_AT)) enterPressed(t);
      apply(t);
      raf = requestAnimationFrame(loop);
    }
    raf = requestAnimationFrame(loop);
    return () => cancelAnimationFrame(raf);
  }, []);

  function handlePress() {
    pressAtOverrideRef.current = true;
  }

  function handleKeyDown(e: { key: string; preventDefault(): void }) {
    if (e.key === "Enter" || e.key === " ") {
      e.preventDefault();
      pressAtOverrideRef.current = true;
    }
  }

  return (
    <div className={styles.stage}>
      <section className={styles.panel}>
        <div className={styles.card} ref={cardRef}>
          <div
            className={styles.placeholder}
            ref={placeholderRef}
            role="button"
            tabIndex={0}
            aria-label="재생 항목 불러오기"
            aria-pressed="false"
            onClick={handlePress}
            onKeyDown={handleKeyDown}
          >
            <span className={styles.playIcon} aria-hidden="true" />
            <span className={styles.phLabel}>눌러서 불러오기</span>
            <span className={styles.phSub}>약 0.5MB 절약</span>
            <span className={styles.hintArrow} ref={hintArrowRef} aria-hidden="true" />
          </div>
          <div className={styles.frame} ref={frameRef} aria-hidden="true">
            <canvas className={styles.frameThumb} ref={frameThumbRef} width={240} height={120} />
            <div className={styles.frameScrim} />
            <div className={styles.frameContent}>
              <span className={styles.framePlay} aria-hidden="true" />
              <span className={styles.frameLabel}>불러온 영상 프레임</span>
            </div>
            <div className={styles.progressTrack}>
              <div className={styles.progressBar} ref={progressBarRef} />
            </div>
          </div>
        </div>
        <div className={styles.readout} aria-live="polite">
          <span className={styles.readoutLabel}>현재 높이</span>
          <span className={styles.readoutValue} ref={heightValueRef}>0px</span>
        </div>
      </section>
    </div>
  );
}